Stage-cementing tools, or differential valve (DV) tools, are used to cement casing sections behind the same casing string, or to cement a critical long section in multiple stages. Stage cementing may reduce mud contamination and lessens the possibility of high filtrate loss or formation breakdown caused by high hydrostatic pressures, which is often a cause for lost circulation. In a multi-stage cementing process, a first (or bottom) cement stage is pumped through a cementing tool to the end of the casing and up an annulus to a calculated-fill volume (e.g., height). Then, a shutoff or bypass plug can be dropped or pumped in the casing to seal the first stage. Next, a free-fall or pump-down plug may be used to hydraulically set and open the stage tool (e.g., lower most in the case multiple stage tools are used), allowing the second (or top) cement stage to be displaced above the stage tool (e.g., lower most in the case multiple stage tools are used). A closing plug is then pumped down to close the stage tool (e.g., lower most in the case multiple stage tools are used) to keep cement from U-tubing above and back through the tool. In the event an additional (upper) stage tool is used, the above process repeats itself with the exception that only a free fall plug is used to hydraulically set and open the stage tool, allowing for the third cement stage to be displaced above the upper stage tool. Often, stage cementing tools do not open or close properly when using pumped or dropped plugs. Further, there may be leakages of cement around the plugs and through the stage tools.